The present invention relates generally to irrigation techniques, and more specifically to low volume irrigation systems and methods.
Because of increasing water shortages in agricultural areas, there has been used in the past techniques known as "low volume irrigation". Low volume irrigation techniques employ small volumes of water which are generally emitted adjacent the base of the agricultural plants. In some low volume irrigation systems, a central water distribution line is buried underground down a row, with individual low volume trickle emitters or micro spray jets being fed through tubing from the central line via individual lines for irrigation at the ground level of each plant or group of plants.
There are some agricultural plots, such as grape vineyards and apple orchards, because of the root structure and growing pattern of the plants, do not lend themselves well to a buried feedline-type of low volume irrigation system. Accordingly, in those situations it is known to run the central irrigation distribution tube above the base of the plants in a grape vineyard or apple orchard, with low-volume sprinklers or emitters hanging downwardly from the central distribution tube line. In use, these types of vertically hanging low volume arrangements sprinkle the water downwardly onto the base of the plants for irrigation. Since it is customary to run the central distribution tube directly down the row of plants via stakes immediately adjacent to the grape plant or apple tree, then a hanging low volume sprinkler assembly connected to the distribution tube will generally direct the water downwardly to the base of the plant in the intended manner. However, it is customary to employ a thin wall plastic tube for the central distribution line. Because of weather and other conditions, such distribution tubes will often twist or turn about their own axial direction. As a result, many of the hanging low volume sprinkler assemblies will be displaced from the desired position to give the maximum irrigation benefit to the base of the adjacent plants
The vertical hanging low volume sprinkler assemblies used in the past have employed plastic tubing made from the same material as the distribution tube, and is relatively stiff; therefore, any axial twisting of the central feedline tends to exacerbate the displacement of the desired spray pattern, because the stiffness of prior art hanging assembly causes the assembly to extend radially outwardly away from the desired downward direction.
FIGS. 1 and 2 illustrate the above-described difficulties with prior art overhead, vertically hanging low volume irrigation systems. In FIG. 1, a prior art system is referred to generally by the reference numeral 10, and is used for example, to irrigate a grape vineyard, including grape vines 12. Associated with each vine 12 is a stake 14 to which is attached a central distribution tube 16 fabricated of a thin wall plastic material; typically, the plastic, usually comprises polyethylene. A plurality of low volume hanging spray assemblies are attached to the horizontal distribution tube 16, each assembly including an intermediate feed tube 18, a weight 20 and a sprinkler or emitter 22. Desirably, each hanging assembly extends downwardly between two of the grapevines 12, and thus is capable of irrigating the base of two adjacent plants.
However, as is shown with two of the assemblies on the left hand side of FIG. 1 and in cross section in FIG. 2, often times the central distribution tube 16 is subjected to axial twisting caused by weather conditions, improper installation and the like. Heretofore, the intermediate feed tube 18 has been fabricated in the prior art from materials which are essentially identical to the material of the central distribution tube 16. However, such materials are relatively stiff, even when the weight 20 is attached at the end of the assembly adjacent the emitter 22. As a result, the axial twisting of the central distribution tube 16 causes the relatively stiff intermediate tubes 18 to extend outwardly as shown in FIG. 2, thus dislocating the desired spray pattern 24 in the manner shown in FIG. 1. As a consequence, efficiency of the irrigation system is markedly reduced.